It is generally not considered safe to leave Christmas tree lights on all night, especially when you’re asleep or out of the house. Most safety experts recommend turning them off after a few hours and definitely before bed to reduce fire risk.

Core safety answer

  • Fire and electrical organizations advise unplugging or switching off Christmas tree lights overnight and whenever you leave home.
  • A practical rule many experts suggest is using indoor tree lights for about 6–8 hours at a time, only while someone is awake and nearby.

Why leaving them on is risky

  • Lights can overheat, especially older or damaged strings, which can ignite a dry real tree or dusty artificial branches.
  • Faulty wiring, overloaded outlets, or cheap extension cords can cause short circuits or electrical arcing that start fires silently while you sleep.

LED vs older lights

  • Modern LED tree lights run cooler and are more energy‑efficient than traditional incandescent bulbs, which get much hotter.
  • Even with LEDs, experts still advise turning them off when unattended, because wiring, plugs, and outlets can still fail under continuous use.

Practical safety tips

  • Turn lights off before bed and when leaving the house; use a timer or smart plug so they shut off automatically at night.
  • Inspect light strings yearly, replace any with frayed wires or cracked bulbs, avoid daisy‑chaining too many sets, and don’t overload one outlet or power strip.

If you really want them on late

  • Prefer high‑quality, certified LED lights on a fresh, well‑watered real tree or a flame‑retardant artificial tree, placed away from heaters, candles, and curtains.
  • Make sure smoke alarms work and are not blocked by decorations; this is a simple but important extra layer of protection.

TL;DR: Enjoy the cozy look in the evening, but for safety, switch Christmas tree lights off after a few hours and always before you go to sleep. Leaving them on all night is not worth the fire risk.